How Claude Code's entire source code leaked, and it wasn't a hack

Last week, March 31, 2026, Anthropic, the company behind Claude, accidentally leaked the full source code of their product Claude Code. Here's the full story, explained so anyone can follow it. First, what is Claude Code? Claude Code is a tool that developers install on their laptops to use Claude directly from their terminal - their command line. Think of it like an app, but instead of downloading it from an app store, developers install it from a place called npm. npm is basically the App Store for developer tools. When a company like Anthropic wants to ship a tool that developers can install with one command, they publish it to npm. It's public, open, and anyone in the world can download any package from it — no account, no password, no fee. That's by design. It's how the whole ecosystem works. If you write C# npm is NuGet. Publishing to npm is exactly like publishing a package to nuget.org, except every single package on npm is public by default. When Anthropic published Claude Cod